Just wondering if anybody upgraded there Rubicon to a 550, and if you had any trouble with the engine afterwards. I am just in the process of having the sleeve put in, new cam, clutch kit, the carb jetted and wondering about a new muffler. I am not thrilled to have an extremely loud muffler, does anybody know of a muffler that can offer good performance without sounding like a straight pipe.[img]i/expressions/devil.gif[/img]